The present invention relates to luminaires which are supplied with operating power from a primary power source and are equipped with an emergency power source for maintaining lighting for a limited period of time if the primary power source should fail.
In a fluorescent luminaire a ballasting device is required to limit current to the fluorescent lamps. This ballast can be a passive device (e.g. an inductor) or an active circuit that converts the low frequency line voltage input to a high frequency AC output. In addition to the normal AC ballast, another device can be included in the luminaire to provide light for a short period during a loss of line power. This "emergency ballast" is an active circuit that converts energy from a standby power source, such as a rechargeable internal battery, to a voltage and current that is suitable to drive the fluorescent lamp.
Under normal operating conditions, power is provided from power mains to the normal AC ballast to generate light, and to the emergency ballast to maintain a charge on the internal battery. In the event of loss of line voltage, relays in the emergency ballast switch the emergency ballast to the lamp and the circuit provides power to the lamp for a short period, typically 90 minutes.
Since the emergency ballast is not normally operating, it would be desirable to test the ballast periodically to insure that it will function properly when power is lost. This conventionally requires the active intervention of someone to test the device by simulating a power outage and monitoring the operation of the emergency ballast. In many installations this task is neglected and failure of an emergency ballast can only be detected when an emergency situation exists.